RAIM?

[Roy Smith]

I've been doing most of my GPS flying with a CNX-80, which doesn't seem
to suffer from loss of RAIM. Last night I was flying with a GX-60, and
got a RAIM warning when commencing an approach.

The GX-60 manual isn't real illuminating on what you're supposed to do
at this point. Presumably, "continue the approach as if nothing
happened" would not be smart (although, being VFR, that's exactly what
we did last night).

So, what do you do? Ask ATC to hold someplace in the hopes the RAIM
warning goes away as the satellites shuffle around? If so, how long
would you expect this would take? Does the controller know enough about
GPS to understand what I mean if I tell him "I've got a RAIM alert"?

[Matt Whiting]

Roy Smith wrote:
> I've been doing most of my GPS flying with a CNX-80, which doesn't seem
> to suffer from loss of RAIM. Last night I was flying with a GX-60, and
> got a RAIM warning when commencing an approach.
>
> The GX-60 manual isn't real illuminating on what you're supposed to do
> at this point. Presumably, "continue the approach as if nothing
> happened" would not be smart (although, being VFR, that's exactly what
> we did last night).
>
> So, what do you do? Ask ATC to hold someplace in the hopes the RAIM
> warning goes away as the satellites shuffle around? If so, how long
> would you expect this would take? Does the controller know enough about
> GPS to understand what I mean if I tell him "I've got a RAIM alert"?

He's probably ask you why you were worried that it was raining? :-)

Seriously, good question, and I haven't seen this addressed yet in
anything I've read. Must be in the fine print somewhere though.


Matt

[Teacherjh]

>>
Last night I was flying with a GX-60, and
got a RAIM warning when commencing an approach.

The GX-60 manual isn't real illuminating on what you're supposed to do
at this point.
<<

Switch to your backup navigation system, which you've been using all along.
This is one of the reasons why GPS is not authorized as a sole navigation means
(you need to have a backup)

Jose

--
(for Email, make the obvious changes in my address)

[Mick Ruthven]

You have no in-panel backup for a GPS approach not based on a VOR or some
other navaid. And that's authorized. If the RAIM warning persists you'd have
to treat it as navigation-equipment failure and discontinue the approach and
of course tell ATC. If the missed approach fix is also a GPS-only waypoint,
you'll need vectors to it. If you're not in radar coverage you've got
another problem; you have to know what a safe course of action is
considering the terrain.

"Teacherjh" > wrote in message
...
> >>
> Last night I was flying with a GX-60, and
> got a RAIM warning when commencing an approach.
>
> The GX-60 manual isn't real illuminating on what you're supposed to do
> at this point.
> <<
>
> Switch to your backup navigation system, which you've been using all
along.
> This is one of the reasons why GPS is not authorized as a sole navigation
means
> (you need to have a backup)
>
> Jose
>
> --
> (for Email, make the obvious changes in my address)

[Bob Gardner]

Look to the AIM, not the manual. 1-1-20(j)(3) makes it clear.

Bob Gardner

"Matt Whiting" > wrote in message
...
> Roy Smith wrote:
> > I've been doing most of my GPS flying with a CNX-80, which doesn't seem
> > to suffer from loss of RAIM. Last night I was flying with a GX-60, and
> > got a RAIM warning when commencing an approach.
> >
> > The GX-60 manual isn't real illuminating on what you're supposed to do
> > at this point. Presumably, "continue the approach as if nothing
> > happened" would not be smart (although, being VFR, that's exactly what
> > we did last night).
> >
> > So, what do you do? Ask ATC to hold someplace in the hopes the RAIM
> > warning goes away as the satellites shuffle around? If so, how long
> > would you expect this would take? Does the controller know enough about
> > GPS to understand what I mean if I tell him "I've got a RAIM alert"?
>
> He's probably ask you why you were worried that it was raining? :-)
>
> Seriously, good question, and I haven't seen this addressed yet in
> anything I've read. Must be in the fine print somewhere though.
>
>
> Matt
>

[Roy Smith]

In article >,
"Bob Gardner" > wrote:

> Look to the AIM, not the manual. 1-1-20(j)(3) makes it clear.

Thanks for the reference (although, it looks like it's really 1-1-19,
not 1-1-20, at least in the version I've got). While that does clear
things up a bit, it still leaves one with a bit of head-scratching to do.

The immediate action is clear; continue to fly the approach track, but
do not descend to the MDA, and execute the missed when you reach the
MAWP.

But what then? It says I should contact ATC as soon as practical, but
what do I tell them? Presumably, I start with the obvious, "New York,
3875T, missed approach", but what do I want to do after that? If I just
get vectors back for another shot, is it likely that the condition which
caused the RAIM alert will have resolved itself by then?

Is there a standard phrasology for telling the controller you had a RAIM
alert? It seems like there should be some compact way to say, "I had a
problem with my GPS equipment, but don't worry, it'll fix itself in a
little while".

[Bob Gardner]

Tracking those section and subsections makes my head ache, but 1-1-19 is
clearly labeled "Doppler Radar" in my 2004 FAR/AIM. In any event, a section
titled "Receiver Autonomous Integrity Monitoring," in subsection (3), tells
the reader that if a RAIM/status annunciation occurs prior to the final
approach waypoint, the approach should not be completed since GPS may no
longer provide the required accuracy." Subsection (4) says: "If the receiver
does not sequence into the approach mode or a RAIM failure/status
annunciation occurs prior to the FAWP the pilot should not descend to MDA
but should proceed to the missed approach waypoint (MAWP) via the FAWP,
perform a missed approach, and contact ATC as soon as practicable."

With the exception of telling us how to pronounce fiver and niner and how to
report altitudes, the AIM is not big on pilot phraseology, as you know. ATCH
tells controllers exactly what to say, with little wiggle room, but pilots
have no similar publication to refer to...and I suspect that that situation
will not change.

Bob Gardner
"Roy Smith" > wrote in message
...
> In article >,
> "Bob Gardner" > wrote:
>
> > Look to the AIM, not the manual. 1-1-20(j)(3) makes it clear.
>
> Thanks for the reference (although, it looks like it's really 1-1-19,
> not 1-1-20, at least in the version I've got). While that does clear
> things up a bit, it still leaves one with a bit of head-scratching to do.
>
> The immediate action is clear; continue to fly the approach track, but
> do not descend to the MDA, and execute the missed when you reach the
> MAWP.
>
> But what then? It says I should contact ATC as soon as practical, but
> what do I tell them? Presumably, I start with the obvious, "New York,
> 3875T, missed approach", but what do I want to do after that? If I just
> get vectors back for another shot, is it likely that the condition which
> caused the RAIM alert will have resolved itself by then?
>
> Is there a standard phrasology for telling the controller you had a RAIM
> alert? It seems like there should be some compact way to say, "I had a
> problem with my GPS equipment, but don't worry, it'll fix itself in a
> little while".

[Teacherjh]

>>
It says I should contact ATC as soon as practical, but
what do I tell them?
<<

Tell them you've had a GPS RAIM alert. You should decide what you want to do,
and tell them what it is. "Request the NDB 23 approach" "Request hold at
ALBEE for four minutes, then another GPS approach" "Request two all beef
patties, special sauce...."

Jose

--
(for Email, make the obvious changes in my address)

[Stan Gosnell]

Roy Smith > wrote in
:

> The GX-60 manual isn't real illuminating on what you're
> supposed to do at this point. Presumably, "continue the
> approach as if nothing happened" would not be smart
> (although, being VFR, that's exactly what we did last
> night).
>
> So, what do you do? Ask ATC to hold someplace in the hopes
> the RAIM warning goes away as the satellites shuffle
> around? If so, how long would you expect this would take?
> Does the controller know enough about GPS to understand
> what I mean if I tell him "I've got a RAIM alert"?

Depends. You do need to tell ATC about it, and they should know
exactly what you're talking about. You can hold, get vectors to
start the approach over, or whatever you want. RAIM warnings
usually go away within a few minutes - I seldom see them last 5
minutes.

--
Regards,

Stan

[Roy Smith]

Stan Gosnell <me@work> wrote:
> RAIM warnings usually go away within a few minutes - I seldom see
> them last 5 minutes.

That's the piece of information I was looking for. Thanks!

[[email protected]]

I've just told them we needed to wait for better satelite geometry,
and gave them a request to hold somewhere. Seems to have been clear
enough. We've held 10 minutes or so both times. the UNS's we have
allow us to predict raim, so that let us know that it should be fine
shortly. It also warned us we could expect the problem beforehand.
Stan
That seems to have bOn Sun, 30 May 2004 08:33:36 -0400, Roy Smith
> wrote:

>we did last night).
>
>So, what do you do? Ask ATC to hold someplace in the hopes the RAIM
>warning goes away as the satellites shuffle around? If so, how long
>would you expect this would take? Does the controller know enough about
>GPS to understand what I mean if I tell him "I've got a RAIM alert"?

[Newps]

"Stan Gosnell" <me@work> wrote in message
...
>
> Depends. You do need to tell ATC about it, and they should know
> exactly what you're talking about.

That's hillarious. The FAA is so far behind GPS it's embarrasing. For
example we have an ILS here that requires DME because the OM and the other
fixes on the LOC approach are DME fixes. When the ILS DME is out of service
for any reason they NOTAM the whole approach out of service. I've been
fighting for a couple years with who ever will listen but to no avail.

[Newps]

"Roy Smith" > wrote in message
...
> Stan Gosnell <me@work> wrote:
> > RAIM warnings usually go away within a few minutes - I seldom see
> > them last 5 minutes.
>
> That's the piece of information I was looking for. Thanks!

And a RAIM warning on an IFR box triggers a light on the panel. When the
light goes out you got your RAIM back.

[Roy Smith]

In article >,
"Newps" > wrote:

> we have an ILS here that requires DME because the OM and the other
> fixes on the LOC approach are DME fixes. When the ILS DME is out of service
> for any reason they NOTAM the whole approach out of service.

What's the approach?

[Newps]

"Roy Smith" > wrote in message
...
> In article >,
> "Newps" > wrote:
>
> > we have an ILS here that requires DME because the OM and the other
> > fixes on the LOC approach are DME fixes. When the ILS DME is out of
service
> > for any reason they NOTAM the whole approach out of service.
>
> What's the approach?


BIL ILS 28R

[John]

Teacherjh wrote:

> >>
> It says I should contact ATC as soon as practical, but
> what do I tell them?
> <<
>
> Tell them you've had a GPS RAIM alert. You should decide what you want to do,
> and tell them what it is. "Request the NDB 23 approach" "Request hold at
> ALBEE for four minutes, then another GPS approach" "Request two all beef
> patties, special sauce...."

You know, holding would be a so much better experience if ATC would provide this
take-out service.

Approach: Beech 32M, number 18 for the approach, hold west of SORRY intersection,
right turns, 8000. Expect further clearance in 35 minutes.

Beech: No problem, Approach. Could you send up some more dogs with special
sauce? Request pick-up at the fix. Our GPS integrity light is on again.

Approach, Roger 32M. Let us know if you require any additional holding time for
lunch.


I say no user fees without take-out.

[Ron Rosenfeld]

On Sun, 30 May 2004 08:33:36 -0400, Roy Smith > wrote:

>I've been doing most of my GPS flying with a CNX-80, which doesn't seem
>to suffer from loss of RAIM. Last night I was flying with a GX-60, and
>got a RAIM warning when commencing an approach.

The CNX80 doesn't do RAIM.


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)

[C J Campbell]

"Teacherjh" > wrote in message
...
> >>
> Last night I was flying with a GX-60, and
> got a RAIM warning when commencing an approach.
>
> The GX-60 manual isn't real illuminating on what you're supposed to do
> at this point.
> <<
>
> Switch to your backup navigation system, which you've been using all
along.
> This is one of the reasons why GPS is not authorized as a sole navigation
means
> (you need to have a backup)

All of this is wrong.

[C J Campbell]

WAAS GPS units do not use RAIM. For missed approach procedures in the event
of loss of RAIM, this is from chapter 1 of AIM:

3. If a RAIM failure/status annunciation occurs prior to the final approach
waypoint (FAWP), the approach should not be completed since GPS may no
longer provide the required accuracy. The receiver performs a RAIM
prediction by 2 NM prior to the FAWP to ensure that RAIM is available at the
FAWP as a condition for entering the approach mode. The pilot should ensure
that the receiver has sequenced from "Armed" to "Approach" prior to the FAWP
(normally occurs 2 NM prior). Failure to sequence may be an indication of
the detection of a satellite anomaly, failure to arm the receiver (if
required), or other problems which preclude completing the approach.

4. If the receiver does not sequence into the approach mode or a RAIM
failure/status annunciation occurs prior to the FAWP, the pilot should not
descend to Minimum Descent Altitude (MDA), but should proceed to the missed
approach waypoint (MAWP) via the FAWP, perform a missed approach, and
contact ATC as soon as practical. Refer to the receiver operating manual for
specific indications and instructions associated with loss of RAIM prior to
the FAF.

5. If a RAIM failure occurs after the FAWP, the receiver is allowed to
continue operating without an annunciation for up to 5 minutes to allow
completion of the approach (see receiver operating manual). If the RAIM
flag/status annunciation appears after the FAWP, the missed approach should
be executed immediately.

[Stan Gosnell]

"Newps" > wrote in
:

> And a RAIM warning on an IFR box triggers a light on the
> panel. When the light goes out you got your RAIM back.

Well, that depends. On our Trimble boxes we get a flashing
message light, and you have to check the message page to see
what happened. Then when RAIM comes back, we get another
flashing message light. The message light is annoying, because
it comes on for lots of things, many of them unimportant, some
of more importance. The Trimble units are really poorly
designed, and I would prefer almost anything else, but I don't
get a choice in any of this.

--
Regards,

Stan

[Javier Henderson]

Roy Smith > writes:

> I've been doing most of my GPS flying with a CNX-80, which doesn't seem
> to suffer from loss of RAIM. Last night I was flying with a GX-60, and
> got a RAIM warning when commencing an approach.
>
> The GX-60 manual isn't real illuminating on what you're supposed to do
> at this point. Presumably, "continue the approach as if nothing
> happened" would not be smart (although, being VFR, that's exactly what
> we did last night).
>
> So, what do you do? Ask ATC to hold someplace in the hopes the RAIM
> warning goes away as the satellites shuffle around? If so, how long
> would you expect this would take? Does the controller know enough about
> GPS to understand what I mean if I tell him "I've got a RAIM alert"?

There was a thread about this on the CPA web based forum. The gist of
it was that there were issues with the GX50/GX60, related to the GPS
engine. If memory serves, UPSAT came up with a fix. Of course, Garmin
now owns the UPSAT line and the GX line has been discontinued, so
who knows. Call Garmin.

Unfortunately, the terms of use of the CPA web forum prevent me from
quoting the entire thread here.

-jav

[S Green]

"Roy Smith" > wrote in message
...
> I've been doing most of my GPS flying with a CNX-80, which doesn't seem
> to suffer from loss of RAIM. Last night I was flying with a GX-60, and
> got a RAIM warning when commencing an approach.
>
> The GX-60 manual isn't real illuminating on what you're supposed to do
> at this point. Presumably, "continue the approach as if nothing
> happened" would not be smart (although, being VFR, that's exactly what
> we did last night).
>
> So, what do you do? Ask ATC to hold someplace in the hopes the RAIM
> warning goes away as the satellites shuffle around? If so, how long
> would you expect this would take? Does the controller know enough about
> GPS to understand what I mean if I tell him "I've got a RAIM alert"?

implement plan B or C which does not need GPS

[Dave Butler]

Roy Smith wrote:
> I've been doing most of my GPS flying with a CNX-80, which doesn't seem
> to suffer from loss of RAIM. Last night I was flying with a GX-60, and
> got a RAIM warning when commencing an approach.
>
My subjective observation (is that the GX50/60 has more difficulties with RAIM
than other GPS receivers. IIRC the manual tells you to expect one in every 20
approaches, or maybe it says 5 percent of the time, or something like that.
People that fly behind other receivers seem never to get RAIM warnings.

Dave
Remove SHIRT to reply directly.

[John Bell]

> Tracking those section and subsections makes my head ache, but 1-1-19 is
> clearly labeled "Doppler Radar" in my 2004 FAR/AIM.

Bob,

The latest AIM is available online at http://www.faa.gov/ATpubs/AIM/.

John Bell

[Jerry Kurata]

How old is the database on the GX60? There were reports of GX database bugs
causing RAIM errors 3-6 months ago. Supposedly later additions of the
database have resolved this error. Also, does the GX-60 have a RAIM status
page? I usually do a RAIM check an hour or so out on the GNS430.

jerry

"Roy Smith" > wrote in message
...
> I've been doing most of my GPS flying with a CNX-80, which doesn't seem
> to suffer from loss of RAIM. Last night I was flying with a GX-60, and
> got a RAIM warning when commencing an approach.
>
> The GX-60 manual isn't real illuminating on what you're supposed to do
> at this point. Presumably, "continue the approach as if nothing
> happened" would not be smart (although, being VFR, that's exactly what
> we did last night).
>
> So, what do you do? Ask ATC to hold someplace in the hopes the RAIM
> warning goes away as the satellites shuffle around? If so, how long
> would you expect this would take? Does the controller know enough about
> GPS to understand what I mean if I tell him "I've got a RAIM alert"?

[[email protected]]

C J Campbell wrote:

> "Teacherjh" > wrote in message
> ...
> > >>
> > Last night I was flying with a GX-60, and
> > got a RAIM warning when commencing an approach.
> >
> > The GX-60 manual isn't real illuminating on what you're supposed to do
> > at this point.
> > <<
> >
> > Switch to your backup navigation system, which you've been using all
> along.
> > This is one of the reasons why GPS is not authorized as a sole navigation
> means
> > (you need to have a backup)
>
> All of this is wrong.

All of what is wrong?